A gas-cooled electric machine (cf. USSR Inventor's Certificate No. 509,947 issued on Feb. 16, 1973) is known to comprise a rotor and a stator which has a core with radial ducts and slots on its inside surface, a winding arranged in the slots of the stator core, and slot wedges having projections located in the stator-to-rotor air gap lengthwise the axis of the electric machine involved.
The projections of the slot wedges decelerate the flow of gas rotating along with the rotor, thus adding to the gas flow velocity relative to the rotor. This, however, impairs stator cooling conditions owing to a reduced gas flow velocity with respect to the stator and the resultant drop of the rate of gas flow through the radial ducts.
Another prior-art gas-cooled electric machine (cf. USSR Intentor's Certificate No. 550,723, cl.H02K 3/48, issued 1960) is known to comprise a rotor and a stator which has a core with radial ducts and slots on its inside surface, a winding arranged in the slots of the stator core, and slot wedges having projections located in the stator-to-rotor air gap lengthwise the axis of the electric machine under consideration.
Projections that protrude into the stator-to-rotor air gap feature longitudinally alternating cross slots and teeth.
In the abovesaid gas-cooled electric machine the teeth of the wedge projections decelerate the tangentially rotating gas flow, thus increasing the gas flow velocity relative to the rotor and providing an efficient cooling of the rotor, while the slots in the wedge projections eliminate the zones with a higher gas pressure in the air gap and, hence, stator overheating.
However, there remain some zones in the stator, arranged oppositely to the wedge projections, wherein overheating occurs, which affects adversely stator cooling; at the same time rotor cooling is but of an inadequate efficiency as the wedge projections are not provided throughout the stator length.
Moreover, the assembling procedure of the above-said known gas-cooled electric machine is difficult due to a necessity to accurately fit the rotor into the stator so as to preserve intact the wedge projections.